Ambient Synthesis of Single‐Atom Catalysts from Bulk Metal via Trapping of Atoms by Surface Dangling Bonds

Single‐atom catalysts (SACs) feature the maximum atom economy and superior performance for various catalysis fields, attracting tremendous attention in materials science. However, conventional synthesis of SACs involves high energy consumption at high temperature, complicated procedures, a massive waste of metal species, and poor yields, greatly impeding their development. Herein, a facile dangling bond trapping strategy to construct SACs under ambient conditions from easily accessible bulk metals (such as Fe, Co, Ni, and Cu) is presented. When mixing graphene oxide (GO) slurry with metal foam and drying in ambient conditions, the M⁰ would transfer electrons to the dangling oxygen groups on GO, obtaining M^δ+ (0 < δ < 3) species. Meanwhile, M^δ+ coordinates with the surface oxygen dangling bonds of GO to form M? O bonds. Subsequently, the metal atoms are pulled out of the metal foam by the M? O bonds under the assistance of sonication to give M SAs/GO materials. This synthesis at room temperature from bulk metals provides a versatile platform for facile and low‐cost fabrication of SACs, crucial for their mass production and practical application in diverse industrial reactions.     

Enrichment and geoaccumulation of metals in the superficial sediments of Lake Chivero,Zimbabwe

Sediments act as a sink, being an integrator and an amplifier for metals in rivers, lakes and reservoirs. Thus, sediment quality has been recognized as an important indicator of aquatic pollution. The concentrations of aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn) and sodium (Na) were studied in the surface sediments of Lake Chivero, Zimbabwe, to determine metal accumulation, distribution, pollution status and to distinguish natural background metal levels from human pollution sources. Sediment samples were collected from 17 locations during a two‐year (2014–2015) monitoring period during the hot–dry, hot–wet and cool–dry seasons. The overall mean metal concentrations exhibited the following decreasing order: Fe > Al>Mn > Ca>K > Mg>Na. The Mn levels for all sites and seasons were above the severe effect level (SEL). The highest metal and enrichment factor (EF) values were observed for the hot–wet season, indicating the period when the reservoir received the highest metal pollution from its catchment. The Geochemical index (I_geo) values for Mn for all seasons indicated moderately to strong contamination in sediments. The pollution load index (PLI) for all seasons indicated low pollution levels. Sediment contamination was attributed to natural sources for Al, Na and K and anthropogenic sources for Fe, Ca, Mg and Mn. The levels of studied metals in the Lake Chivero sediments are comparable to other eutrophic lentic systems. The results of the present study provide baseline information necessary for developing future metal pollution control strategies for Lake Chivero and its catchment.     

Ultra-Uniform Nanocrystalline Materials via Two-Step Sintering

Nanocrystalline materials with superior properties are of great interest. Much is discussed about obtaining nanograins, but little is known about maintaining grain-size uniformity that is critical for reliability. An especially intriguing question is whether it is possible to achieve a size distribution narrower than what Hillert theoretically predicted for normal grain growth, a possibility suggested—for growth with a higher growth exponent—by the generalized mean-field theory of Lifshitz, Slyozov, Wagner (LSW), and Hillert but never realized in practice. Following a rationally designed two-step sintering route, it has been made possible in bulk materials by taking advantage of the large growth exponent in the intermediate sintering stage to form a uniform microstructure despite residual porosity, and freezing the grain growth thereafter while continuing densification to reach full density. The bulk dense Al₂O₃ ceramic thus obtained has an average grain size of 34 nm and a size distribution much narrower than Hillert's prediction. Bulk Al₂O₃ with a grain-size distribution narrower than the particle-size distribution of starting powders is also demonstrated, as are highly uniform bulk engineering metals (refractory Mo and W-Re alloy) and complex functional ceramics (BaTiO₃-based alloys with superior dielectric strength and energy capacity).     

纳滤去除水中的有害离子

本文综述了纳滤去除饮用水和重金属废水中的有毒有害离子的应用研究，阐述了纳滤膜对无机盐的截留效果主要取决于膜对离子的电荷效应，表现在对多价离子的截留率高于单价离子。利用纳滤膜这种分离性能，可以去除部分饮用水中微量的有害单价离子（如NO2^-、NO3^-、F^-等）和大部分的有毒二价离子（如HAsO4^2-和重金属离子），获取优质安全的饮用水；也可以用于处理重金属废水，能有效去除废水中的重金属离子。将纳滤和反渗透集成用于重金属废水处理，可以做到对有毒重金属离子的回收利用和出水回用，实现清洁生产，既具经济效益，又具环境效益，在工程实际中极具推广应用价值。     

菠萝废料提取液在盐酸介质中对A3钢缓蚀性能的研究

本文采用失重法研究菠萝皮、菠萝冠芽提取液(以下简称BLB,BLY)在盐酸溶液中对A3钢的缓蚀性能.实验表明,在50℃,5%HCl中,使用0.5%的BLB、BLY浓缩物(折合鲜汁15%),缓蚀率可达90%以上,缓蚀效率比莲藕汁、橙皮汁、葵树花穗汁等植物缓蚀剂高.BLB、BLY与甲醛、乌洛托品等缓蚀剂具有较好的协同效应.此外还用电化学方法对BLB缓蚀机理进行了初步探讨.     

Evaluation of the degree of Cr ions immobilization by different binders

Disposal of industrial solid wastes can cause environmental risks due to the mobility of toxic elements. Stabilization/solidification (s/s) is an effective tool in the treatment of various wastes; however, there is a lack of chemical fixation on the concentrations of Cr. Thus, Cr, in particular Cr⁶⁺, remains free in the leachate. Some phases of the blast furnace slag seem to be able to exert a solubility control on chromium. This study evaluates the effect of various binders on the fixation of Cr ions. Static leaching tests were conducted at two different water-solid ratios as a means to distinguish elements that have solubility controls. The results show that Cr content decreases very quickly to obtain values near 0.03 ppm soon after the contact between the contaminated solution and the different binders. The sample containing only the slag was the most effective. Cr was evenly distributed in the C-S-H as detected by scanning electron microscope (SEM).     

The Modification of Epoxy/Metal Interphases by Adsorbed Contaminants

The interfacial region formed between an epoxy/polyamide adhesive and three metallic substrates has been investigated using x-ray photoelectron spectroscopy. The effect of adsorbed contaminants on the interfacial region has also been studied. The substrates studied were cold-rolled steel, electrogalvanized steel and 2024 aluminum. A “ship-out” oil was used to contaminate the cold-rolled steel and electrogalvanized steel whereas an aerospace hydraulic fluid was used to contaminate the 2024 aluminum. Preferential adsorption of the curing agent by the substrates was observed, the effect being most marked in the case of the electrogalvanized steel substrates. The interaction between the galvanized steel and the 2024 aluminum and the curing agent was primarily via the free amines in the polyamide curing agent. In the case of cold-rolled steel the interaction occurred via the amide component. Cold-rolled steel and 2024 aluminum protonated the curing agents. No protonation was detected in the case of the electrogalvanized steel substrates due to the formation of a zinc/amine coordination compound involving the lone pairs of electrons on the nitrogen atoms. When the contaminated cold-rolled steel substrates were studied, the adhesive displaced the majority of the ship-out oil, but no protonation of the curing agent was observed. This indicated that some residual contaminant remained associated with the cold-rolled steel substrate. The majority of the ship-out oil was not displaced from the electrogalvanized steel because the strong preferential adsorption of the curing agent by the substrates created an adhesive layer enriched in epoxy. As the epoxy resin was incompatible with the oil, this epoxy-rich layer acted as a barrier, preventing the absorption of the oil by the bulk adhesive. In the case of the 2024 aluminum substrate, the level of preferential adsorption of the curing agent was decreased, but protonation of the nitrogen groups was still observed. These results indicated that the hydraulic fluid was displaced from the 2024 aluminum in some areas.     

Investigation of Pb(II) bioremediation potential of algae and cyanobacteria strains isolated from polluted water

Algae and cyanobacteria are known to be able to remove a variety of pollutants from water, including toxic metal ions. In this study, algal and cyanobacterial species growing in two polluted water bodies were identified, and the Pb(II) removal ability of these isolated species was investigated. Based on microscopic observations, 27 species were identified, and nine species were isolated as pure cultures. Pb(II) bioremediation of five selected species (Anacystis sp., Chlorella sp. 1, Monoraphidium sp., Phormidium sp., and Uronema sp.) was studied in detail. The mean Pb(II) removal abilities varied among these five species: Phormidium sp. > Monoraphidium sp. > Uronema sp. > Chlorella sp. 1 > Anacystis sp. The Pb(II) tolerance of each species was determined based on the live cell percentage and biofilm formation capacity. Within a period of 3 d, Phormidium sp., Monoraphidium sp., and Uronema sp. showed nearly 90% of survival, and all five species demonstrated biofilm formation capacities exceeding 50%. Furthermore, the Pb(II) removal ability of the five species exhibited a strong positive correlation with the live cell percentage and showed a strong negative correlation with the biofilm formation capacity. In conclusion, Phormidium sp., Monoraphidium sp., and Uronema sp. exhibited high tolerances towards Pb(II) and presented high removal abilities. Thus, these species can be identified as potential sorbents for development of suitable adsorption systems to remove Pb(II) from aqueous solutions.     

An overview of gold-catalysed oxidation processes

Gold and gold/platinum group metals (Au/PGM) catalysts are active under mild conditions or even at ambient temperature or less and this makes them unique. They will therefore be effective in reducing running costs of chemical plants and increasing the selectivity of the reactions involved where applicable. In pollution control applications such as air cleaning, low light-off autocatalysts, and purification of hydrogen streams used for fuel cells they have the characteristics to become the catalysts of choice, especially now that their durability and resistance to poisons is being shown to be better than was anticipated. The mechanisms of these gold catalysed reactions are still uncertain but both oxidised and metallic gold are probably involved, and the details depend on types of reaction and the conditions used.     

Method for Processing Metal-Reinforced Ceramic Composites

A new process is developed to form a ceramic containing a three-dimensional network of metal reinforcement. The process involves four steps: (1) forming a powder compact containing a continuous network of either organic or carbon material by pressure filtration, (2) pyrolyzing the network to form channels within the powder compact, (3) densifying the powder while retaining the channel network, and (4) intruding metal into the channel network by squeeze casting. Pressure filtration is used to form the powder compact containing the pyrolyzable network either by mixing slurries of powder with chopped fiber or by packing powder within pyrolyzable preforms. When pressure is removed after filtration, the differential strain recovery of the powder matrix relative to the organic material can cause damage. Such damage is prevalent for a powder matrix formed from flocced slurries. However, this problem is avoided by using dispersed slurries which produce consolidated bodies that alleviate stresses arising from differential strain recovery by viscous flow. Metal-reinforced ceramic composites with different reinforcement architectures, volume fractions, and sizes can be produced with this technique.